(1) HIV Rev is an important regulatory factor required for HIV expression. We have made extensive modifications of the Rev protein in order to improve its solubility for NMR measurements and crystallization trials. In addition, we are attempting to further stabilize Rev for structural studies by forming binary complexes with either antibodies or tubulin. To generate a wider range of monoclonal antibodies for co-crystallization studies, we have made recombinant antibodies based on phage display selection. (2) Nef is a 23 kDa protein essential for the pathogenic properties of HIV. We are continuing to investigate some of the specific protein-protein interactions involving Nef especially involving the HIV-1 transactivating protein Tat. We have used surface plasmon resonance to show a specific and tight binding between these proteins. Using protein engineered variants of Nef and Tat we have prepared complexes for more detailed structural studies (3) HIV protease, a homodimeric protein is essential in the viral life cycle and a major anti-AIDS drug target. Peptides derived from the N- and C-terminal regions of the HIV-1 protease dimer interface, inhibit protease by preventing dimerization. The solubility and cell permeability of the peptides was enhanced by linking the transduction domain of HIV-Tat